钢筋砼结构表面裂缝与钢筋锈蚀关系的探讨

依据有关的试验结果,探讨了钢筋砼结构中砼表面裂缝和钢筋处裂缝宽度及钢筋锈蚀三者之间的关系,并分析了钢筋产生锈蚀的原因,认为以砼表面裂缝宽度作为钢筋锈蚀的度量标准不尽合理,控制钢筋处裂缝宽度防止钢筋的局部锈蚀较为有效     

钢筋混凝土柱钢筋套箍加固试验方法

钢筋套箍加固砼柱后，能对其所包围的核心起约束作用，使之处于三轴受压的后力状态，具有较高的抗压强度和极限压缩变形，此即砼的“套箍强化”。钢筋箍对约束砼抗压强度的增强作用因配箍数量、间距和构造而变化。影响的主要因素之一为约束指标λt。通过模拟工程结构投入使用前先进行加固和使用过程中出现裂缝后进行加固两种工程状况试验，可得到钢筋套箍加固柱的受力性能和承载力建议计算公式。     

芯柱在砌块砌体水平承载中的作用试验研究

本试验对页岩陶粒砼小型砌块砌体在水平荷载作用下的承载能力进行了研究,试验做了三个砂浆等级三类砌体共计18个试件。通过对页岩陶粒砼砌块砌体无砼芯柱、有素砼芯柱和有插筋砼芯柱三类砌体,在水平荷载作用下承载能力的研究,得出三种砌体承载能力间定量的关系,插筋砼芯柱砌体水平承载力平均可提高167.13％,并得出三种砌体的破坏形态分别为：沿水平灰缝形成贯通裂缝破坏,砼芯柱在水平灰缝处被剪断而破坏和砌块本身产生裂缝而破坏,旨为制定页岩陶粒砼砌块砌体设计和施工规范提供参考。     

谈确保大体积砼的施工安全

随着建筑业的快速发展,高层建筑物,高耸结构及大型设备基础大量的出现大体积砼已经被广泛应用,大体积砼与普通钢筋砼相比,具有结构厚,体形大,钢筋密,砼数量多,工程条件复杂等特点,因此对施工技术提出了更高的要求,只有重视大体积砼的施工问题,避免裂缝的产生,才能确保施工质量.本文从材料的选用、施工方法、提高施工质量的途径等方面进行简单的论述.     

渠道砼衬砌体裂缝的成因及预防

在灌区节水项目建设中,渠道砼衬砌占有重要地位。砼的早期裂缝和运行过程的裂缝是常出现的问题。渠道砼裂缝成为影响工程质量乃至工程寿命的重要因素,笔者通过近年在宝鸡峡大小渠道处砼衬砌施工的实践,认为夯实好基础是保证砼不裂缝的前提,把好材料进料关是防止砼不裂缝的保证,正确选择好水灰比和骨料比及搅拌、振捣是砼衬砌的重要环节,原浆收面二次压光是减少蜂窝、麻面和早期裂缝的手段,科学合理的分缝是避免运行过程中防止裂缝的必要措施,抓好砼早期养护是提高砼质量避免裂缝的有力保障。     

浅谈钢筋工程施工要点

针对钢筋在砼结构中的重要性,详细地阐述了钢筋工程施工前和施工中的质量控制要点,以提高钢筋工程的施工质量、保证砼结构的安全.     

论商品混凝土楼板裂缝的成因和防治

楼板裂缝,已引起了诸多业主的不满和投诉.经过调查可知,当前现浇砼楼板裂缝基本为砼收缩变形裂缝,所以只要我们能把现浇商品砼楼板收缩变形裂缝的成因弄清楚,就能找预防现浇商品砼楼板变形裂缝的正确途径.     

大体积砼温度裂缝的预防

大体积砼所产生的裂缝的主要形式，为温度裂缝。其裂缝的根本原因是砼的变形。因此，制造合适的允许温差，加强施工中的温度观测，采取适当的温度控制措施，提高砼的极限拉伸强度，以预防大体积砼的温度裂缝。     

住宅地下室的质量事故及加固处理

对某住宅楼地下室墙体及砼构件出现的裂缝进行了调查,通过现场实体检测表明:地下室部分墙体砂浆强度和砼构件的砼强度不足是导致裂缝的主要原因。通过方案比较,提出了安全可靠、经济实用的加固方案。     

大体积砼裂缝产生的原因及防治

大体积砼裂缝问题是建筑工程中的一项质量通病。本文分析了裂缝形成的原因，对设计，材料，施工等方面提出一些预防大体积砼裂缝的想法及处理措施。     

Numerical Determination of Shear Strength of Steel Reinforced Concrete Column Strengthened by CFRP Sheets

The earthquake-resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree,In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon-fiber-reinforced plastic(CFRP) sheets including bond-slip of the anchored reinforcing bars at the foot of the columns is presented.It is based on the yield design theory with a mixed modeling of the structue,according to which the concrete material is treated as a classical two-dimensional continuum ,whereas the longitudinal reinfocing bars are regarded as one-dimensional rods including bond-slip at the foot of the columns,In shear reinforced zones both the shear CFRP sheets and transvers reinforcing bars are incorporated in the analysis throuth a homogenization procedure and they are only in tesion ,The approach is then implemented numerically by means of the finite-element formulation,The numerical procedure produces accurate estimates for the loading-carrying capactiy of the shear members taken as an illustrative application by correlation with the experimental results,so the proposed approach is valid.     

Modeling of Normal Perforation of Reinforced Concrete Slabs by a Rigid Projectile

An analytical model on the normal perforation of reinforced concrete slabs is constructed. The effect of reinforcing bars is further hybridized in a general three-stage model consisting of initial cratering, tunnelling and shear plugging. Besides three dimensionless numbers, i. e., the impact function I, the geometry function of projectile N and the dimensionless thickness of concrete target X, which are employed to predict the ballistic performance of perforation of concrete slabs, the reinforcement ratio Ps of concrete and the tensile strength fs of reinforcing bars are considered as the other main factors influencing the perforation process. Simpler solutions of ballistic performances of normal perforation of reinforced concrete slabs are formulated. Theoretical predictions agree well with individual published experimental data.     

Modeling of Normal Perforation of Reinforced Concrete Slabs by a Rigid Projectile

An analytical model on the normal perforation of reinforced concrete slabs is constructed. The effect of reinforcing bars is further hybridized in a general three-stage model consisting of initial cratering, tunnelling and shear plugging. Besides three dimensionless numbers, i. e. , the impact function /, the geometry function of projectile N and the dimensionless thickness of concrete target X, which are employed to predict the ballistic performance of perforation of concrete slabs, the reinforcement ratioρs of concrete and the tensile strength fs of reinforcing bars are considered as the other main factors influencing the perforation process. Simpler solutions of ballistic performances of normal perforation of reinforced concrete slabs are formulated. Theoretical predictions agree well with individual published experimental data.     

Static and dynamic behavior of concrete slabs reinforced with chemically reactive enamel-coated steel bars and fibers

In this study, the effect of steel fibers coated with chemically reactive enamel (CRE) on the system response of concrete structures with reinforcing bars has been investigated for the first time. In particular, the ultimate strength, ductility, and failure mechanism of 24 reinforced concrete slabs were experimentally characterized under static and blast loads. CRE coating applied on steel bars reduced the crater area of slabs under blast loads by up to 20%; it slightly increased the strength of slabs and significantly reduced the strength degradation of slabs when increasingly deflected under static loads, making the slabs more ductile. CRE coating applied on steel fibers increased the strength of slabs by up to 16% under static loads. The influence of CRE coating applied on both steel fibers and bars may be taken into account by introducing a coating factor in the range of 0.57<β<1.0 in the American Concrete Institute (ACI) development length equation.     

腐蚀对钢筋力学性能影响的试验研究

本通过将混凝土结构用钢筋放置于腐蚀介质(PH=4～5弱酸性溶液)环境中，对不同腐蚀程度的钢筋进行强度和伸长率等力学性能试验，并将试验结果与未经腐蚀的钢筋对比，探讨腐蚀对钢筋力学性能的影响。     

Response of Box-Type Structures Under Internal-Blast Loading

The tests of box-type structures under internal-blast loading are carried out. Then a numerical analysis of the test structures is done using a fully coupled numerical finite element model. The break-up process of the structure is simulated. The failure modes of the simulated structure agree well with the experimental results. The effects of the size of the reinforcing bars and the detailing of connections among the rebars in the concrete on the throw velocity of the fragments are discussed.     

圆筒仓仓壁环向配筋的简化计算

圆筒仓仓壁设计工作历来繁重。根据国家现行设计规范中的有关公式,结合在实际工作中取得的经验,分析了钢筋直径与满跳裂缝、强度要求的含钢率之间的关系,研究出一种较为简便的计算方法,做出了几个主要指标的比值表和曲线图,为经济合理地选用钢筋提供了有利条件。     

Bond property test of reinforced concrete with all soaking and impressed current method corrosion

In order to research the bond properties between corroded reinforcement bars and concrete, reinforcement bars with different diameters and different types and concrete with different strength levels were treated specially with all soaking and impressed current method, and the bond properties were measured with the pull-out test. The comparative analysis of the bond properties of corroded reinforcement bars was carried out. The results showed that the types of reinforcement bars and concrete had great influence on the bond strength. The corrosion and volume expansion of reinforcement bars made concrete in tensile condition, which tended to produce cracks in parallel reinforced direction. The typical bond failure of plain reinforcement bars was pull-out, while the typical bond failure of ribbed reinforcement bars was split. The bond strength between corroded reinforcement bars and concrete increased with the increase of concrete strength. The bond strength of plain and ribbed reinforcement bars showed a decreasing trend after the first increase with the increase of the extent of corrosion. Through the test, the coefficients of the bond strength of plain and ribbed reinforcement bars were given, respectively.     

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bars

Carbon fiber reinforced polymer(CFRP)bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC)beams of a 21-year-old bridge in China.The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory.The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit.The field construction processes of strengthening with CFRP bars-including grouting cracks,cutting groove,grouting epoxy and embedding CFRP bars,surface treating,banding with the U-type CFRP sheets,releasing external prestressed steel tendons-were introduced in detail.In order to evaluate the effectiveness of this strengthening method,field tests using vehicles as live load were applied before and after the retrofit.The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge,including the bending strength and stiffness,is enhanced.The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges.Therefore,the proposed strengthening technology is feasible and effective.     

One and two dimensional chloride ion diffusion of fly ash concrete under flexural stress

A preloading frame is firstly designed to accurately apply external flexural stress to concrete specimens. Then a method is developed to measure one and two dimensional (1D and 2D) chloride ion concentrations at different distances from the surface of concrete under flexural stress. Using this method and the preloading frame, 1D and 2D stress-diffusion is systematically investigated for fly ash concretes made with different fly ash contents (0%, 10%, 20%, 40%, and 60%), and water to binder ratios (0.3, 0.35, and 0.4). The stress accelerating effect on 1D and 2D chloride ion diffusion is also quantitatively analyzed through a comparison between stress-diffusion and nonstress-diffusion. A diffusion accelerating effect caused by external flexural stress can clearly be observed through the comparison. In order to quantify the stress accelerating effect, a stress accelerating factor is proposed in this paper. The relationship between stress accelerating factor and external stress-to-ultimate stress ratio is given as an exponential function. Finally, the process of the initiation, prorogation, and distribution of microcracks on the tensile face of specimen is observed in-situ by using a small-sized loading frame and scanning electron microscope (SEM). The above research provides an insight into chloride attack on the edge reinforcing bars of concrete structures under flexural stress, such as large-span beam and board in the field of civil engineering.